Koalas sleep or rest for up to 22 hours every day to save energy.

Eucalyptus leaves contain chemicals called phenols and terpenes that are toxic to most animals. A koala's liver produces special enzymes to break these poisons down so they do not get sick. They also have a 2-meter long organ called a caecum to help ferment and digest the tough leaf fibers.Even with these tools, eucalyptus provides very little nutrition. Koalas get about 10% of the energy that other plant-eating animals get from their food. To survive on this low-energy diet, koalas have a very slow metabolism. This means their bodies burn fuel much slower than other mammals of the same size.Research from the University of Queensland shows that koalas spend almost all their time inactive. They only spend about 4 minutes a day on high-energy activities like social interaction. Their brains are also small to save even more energy. They get most of their water from the leaves they eat so they rarely need to find a place to drink.An adult koala eats between 400 and 1,000 grams of leaves daily. They choose from about 100 specific types of eucalyptus trees. Their thick fur helps keep them warm so they do not waste energy staying heated. This lifestyle allows them to eat food that other animals cannot touch.